Fertility Analysis

To further understand the the composition of our soil, we looked at the pH and the levels of phosphorus, nitrogen, and potassium present in our soil.

For the pH test, we mixed pH indicator solution and soil together then let it settle for 10 minutes.  

The results of the pH test and the color chart. The top part of the liquid with a bluish-greenish color is what is being compared to the chart.

The pH of our soil was about 6.5, which is just slightly acidic. The ideal pH for grass, which is what mainly grows where this soil was taken from, is between 6.5 and 7. The grass growing in this soil looks healthy, as you can see in our Collecting the Soil post, which makes sense because the pH is right on target.

For the phosphorus test, we mixed soil with Phosphorus Extracting Solution and let it settle. We then used a pipettes to take the clear liquid from the top of the test tube and mixed it with Phosphorus Indicator Reagent. Then one Phosphorus Test Tablet was added and mixed in until it had completely dissolved. The result was compared to the color chart to find that our soil's phosphorus content is lower than the ideal range.

The phosphorus results and color chart.

For the nitrogen test, we mixed soil with Nitrogen Extracting Solution and let it settle. We then used a pipettes to extract the clear liquid from the top and mixed that with Nitrogen Indicator Powder. It was then left to settle and develop for 5 minutes. We found that our soil's nitrogen content was low.

The results of the nitrogen test and the color chart.

For the potassium test, we mixed soil with Potassium Extracting Solution and let it settle. We then extracted the clear liquid from the top with a pipette. We had to repeat the first step in order to get enough clear liquid for the test. We added a Potassium Indicator Tablet to the clear solution and mixed until it had completely dissolved to get the initial purplish color.

 

The initial color of the potassium test.

We then added Potassium Test Solution to the test tube two drops at a time and mixing in between until we saw the color change from purple to blue, as shown below.

It took 18 drops to get the color to completely change from purple to blue. This means that our soil has a low potassium content.